Abstract: A solid state submillimeter wave heterodyne interferometry system and a phase processing method 
based on all phase Fast Fourier Transform (apFFT) are developed to measure electron density during the HL-2M 
first plasma discharges. This system produces the detection wave with the power above 0.1MW and the frequency 
of 306.9GHz by high order frequency multiplication to low frequency phase locked microwave source via planar 
diode frequency multiplying technology. A numeral algorithm for phase calculation based on apFFT is introduced, 
which is able to obtain phase information from raw signals and alleviate phase jump induced by possible high 
lever density fluctuation. The time resolution for the system is 5μs while the lower and upper limits of electron 
density measurement are1016m−3and 1020m−3 respectively. During the HL-2M initial discharges, the system is 
installed on the mid-plane while interferometric measurement is realized by reflection of the metal inner wall, and 
the line-averaged electron densities have been measured. 

Key words: HL-2M tokamak, Solid state sub-millimeter wave interferometer, All phase fast Fourier transform 

摘要： 发展了一套固态亚毫米波外差干涉系统和一种基于全相位快速傅里叶变换(apFFT)的相位处理方法用
于测量 HL-2M 初始等离子体电子密度。该系统采用平面型二极管倍频技术对低频的锁相微波源进行高次倍频以
产生功率大于 0.1MW、频率 306.9GHz 的探测波。基于 apFFT 的相位处理数值算法可以从原始信号中提取相位信
息，缓解由可能的高水平密度扰动导致的相位跳变。系统的固有时间分辨率为 5μs，电子密度测量范围在
10¹⁶~10²⁰m⁻³。在 HL-2M 装置首次实验期间，该系统被安装在中平面上，利用装置内壁反射实现干涉测量，成功
测量了线平均电子密度。 

关键词: HL-2M 装置；固态亚毫米波干涉仪；全相位快速傅里叶转换